Diamond Field-emission Cathodes

Abstract

Summary form only given. Diamond has several properties that give it unique advantages for use in field-emission cathodes. Diamond is the only known air-stable negative electron affinity (NEA) material. This NEA property may allow for field emission at very low electric fields. The inherent structural integrity of the covalently bonded carbon lattice in diamond makes possible more stable cathodes than can be obtained with metals. This presentation reports on initial experiments with diamond field-emission cathodes. Electron emission was characterized from both smooth and patterned regions on p-type, boron-doped homoepitaxial grown diamond on (100)-, (110)-, and (111)-oriented substrates. The measurements indicated a Fowler-Nordheim mechanism (tunneling through a barrier) with the effective barrier height varying as a function of the crystal orientation. The (100) crystals exhibited the largest barrier and the (111) crystals had the smallest barrier. Surface treatment with Cs improves emission and is not adversely affected by exposure to room air. Lithographically defined cathodes with grid structures have been fabricated and emit current near the minimum theoretical grid voltage, 5 V. These cathodes have emitted current densities of >10 A/cm/sup 2/ into vacuum with grid voltages less than 100 V.